Our goal is to develop and test a novel donor-specific, genomic approach to the non-invasive, early diagnosis of rejection and graft dysfunction after solid organ transplantation, and addresses two targeted thematic areas: 1) Applying Genomics and Other High Throughput Technologies;2) Translating Basic Science Discoveries into New and Better Treatments. Organ transplantation saves the lives of patients with end-stage organ failure, yet in many cases, the transplanted organ is rejected by the recipient, causing a life-threatening situation. Previous attempts to develop a non-invasive marker of graft rejection have focused on recipient-specific immune responses, and thus have inherent limitations in sensitivity and specificity, especially for distinguishing rejection from infection. Our novel approach is the first to focus on a donor-specific marker of acute rejection. We will use high throughput next generation sequencing to monitor the proportion of cell-free donor DNA to recipient DNA, in the recipient's blood stream as a marker of rejection. This approach is enabled by the fact that an organ transplant is also effectively a genome transplant, and by monitoring single nucleotide polymorphisms that are specific to the donor's genome one can measure the relative health of the transplanted organ. RATIONALE/HYPOTHESIS: during rejection, apoptosis of donor cells releases donor DNA into the recipient circulation;this DNA can be distinguished from recipient DNA and quantified using high-throughput sequencing techniques;and dynamic changes in donor DNA levels will predict (a) acute rejection;(b) graft dysfunction;and (c) chronic rejection. PRELIMINARY STUDIES: using banked blood samples from heart transplant recipients, we showed that donor DNA levels rise during episodes of acute rejection but remain at stable, low levels in the absence of rejection. AIM 1: Develop a donor DNA monitoring approach for the non-invasive detection of allograft rejection. We will develop and test: (1) next generation DNA sequencing methods to perform low cost, noninvasive analysis of donor DNA load;(2) bioinformatic algorithms that maximize the sensitivity to discriminate donor and recipient DNA;(3) sensitivity of a defined single nucleotide polymorphism (SNP) panel that differentiates donor from recipient. AIM 2: Evaluate the utility of donor DNA monitoring for detection of clinical events (acute rejection, chronic rejection, and graft dysfunction) after heart transplantation. We will conduct a prospective cohort study of 110 consecutive heart transplant recipients, collecting blood samples during and between endomyocardial biopsy (EMB) procedures (yielding 1,516-paired EMB/blood) to determine whether donor:recipient DNA ratio can detect rejection in its early stages and before the development of graft dysfunction. AIM 3: Test this approach in lung transplantation and determine whether donor:recipient DNA ratio can differentiate between graft dysfunction due to rejection versus pulmonary infection. If achieved, these specific aims will provide the foundation for validation studies of a donor-specific, genome-based approach to non-invasive, early detection of rejection after solid organ transplantation. PUBLIC HEALTH RELEVANCE: Organ transplantation saves the lives of patients with end-stage organ failure, yet in many cases, the transplanted organ is rejected by the recipient, causing a life-threatening situation. We propose to develop and test a new and innovative approach to the non-invasive, early diagnosis of rejection and graft dysfunction after heart and lung transplantation. By simply monitoring the blood of a transplant recipient for level of the donor genome appearing during follow-up after receiving a transplant, we hope to establish a diagnostic tool that has potential to save hundreds of millions of dollars in health care costs annually, and reduce patient morbidity and mortality.